1. Field of the Invention
The present invention relates to a light emitting device manufactured by using a large size substrate and a method for manufacturing thereof.
2. Description of the Related Art
A light emitting device utilizing light emission of an electroluminescent element (a light emitting element) has been attracting attention as a display device with wide viewing angle and low power consumption. In recent years, development for the purpose of mass-production of such the light emitting devices has been carried out.
One of the problems in the mass-production of the light emitting devices is the development of a technique for manufacturing the light emitting devices by using a large size substrate. By using the large size substrate, a large size television and the like can be manufactured. In addition, small light emitting devices that are mounted on small electronic appliances such as cellular phones can be mass-produced by using a large size substrate.
However, a large-scale processing apparatus is required in processing a large size substrate when manufacturing a light emitting device using the large size substrate. Therefore, it is difficult to process the entire surface of the substrate under uniform conditions. When using a substrate made from a material that is easily charged, e.g., glass, charge is easily accumulated in a part of the substrate in plasma processing and so on if the entire surface of the substrate is not processed under the uniform conditions. When the accumulated charge moves through elements during process, a large amount of current flows through a migration path of the charge so that deterioration of the elements is sometimes caused.
In order to reduce the deterioration due to the foregoing electrostatic charge, various measures, e.g., arrangement of a short ring that is connected to an input terminal for transmitting signals to a display portion by a conductive film, have been tried. Additionally, a technique of providing a electrostatic charge absorption pattern made from a film of a wiring layer or an electric capacitance is proposed in Japanese Patent Application Laid-Open No. Hei 6-75246 [Patent document 1] so as to reduce the deterioration of the elements due to the electrostatic charge.
When using the short ring, however, it is difficult to prevent the deterioration of the elements due to electrostatic charge caused in process up to formation of the short ring. Further, unnecessary portions after fabricating elements thereover are caused in the technique disclosed in the patent document 1, and hence, the entire surface of the substrate cannot be utilized effectively.